1. Field of the Invention
The invention relates to devices for servicing automotive systems such as automobile air conditioning systems and more specifically to devices allowing the ordinary consumer to measure pressure in automobile air conditioner and charging same with refrigerant.
2. Description of Related Art
Automobile air conditioners, like most air conditioners, use gaseous chemicals called refrigerants to cool air. In accordance with Gay-Lussac's Law, which isP/T=P′/T′ where V is constant  (1)and where P=pressure, T=temperature, V=volume, as the pressure of a compressed gas increases, its temperature increases. Similarly, as the pressure of the gas decreases, the temperature of the gas decreases. In this manner, gas is compressed and then expanded, and air is blown over that portion of the system in which the gas is expanded, and thus the blown air is cooled. This is the basic concept of most refrigeration and air conditioning systems.
Since the pressure of the refrigerant plays an integral part of how efficiently an air conditioning system functions (or if it functions at all), it is desirable to be able to check the pressure of the refrigerant in the air conditioning system to insure that sufficient refrigerant is present. If the system pressure is too low, there will not be sufficient gas to compress and then expand, and the resultant change in temperature will be decreased; the air blown over the cooled portion of the system will, in turn, not be cooled sufficiently. Because the system is subject to significant swings in temperature and frequent thermal cycling—owing both to the action of the air conditioner as well as from the heat of the engine—, joints have a tendency to expand and contract, and refrigerant can slowly leak out of a system over time, even without the presence of a serious breach in the integrity of the system. Also, in an air-conditioning system, the hoses are slightly R-134a-permeable, and the refrigerant will slowly leak out of the hose itself. This was not a problem when air conditioners were running on R-12, since R-12 has a larger molecule than R-134a and leaked less frequently. One must keep a vigilant eye on the refrigerant level in one's automobile air conditioner for the air conditioner to function at optimal levels.
Typical automotive air conditioners are provided with at least one service port to allow for the addition of refrigerant and other chemicals as well as to allow a qualified mechanic to check the level of the refrigerant in the system. There are, however, many automobile owners who choose to perform routine maintenance on their vehicles themselves. This market is commonly referred to as the “do-it-yourself” market, for self-evident reasons.
A standard tool for servicing automobile air conditioners is a set of manifold gauges. This device usually includes three hoses and two gauges: one hose connects to the low pressure service port, one hose connects to the high pressure service port, and the third hose connects to the source of refrigerant. The two gauges measure the pressure at the high and low pressure service ports, respectively. One must know the approximate ambient temperature and look up the pressure readings of the gauges on a chart to determine if there is sufficient refrigerant in the system. Manifold gauges are the standard tool for professional auto mechanics, but they are not popular with do-it-yourself consumers, as they are very complicated to use. Moreover, an amateur should not be opening and using the high pressure service port of the auto air conditioner since there is a much greater risk of injury than with the low pressure side.
A number of products have been developed by the assignee of the instant invention that allow the do-it-yourselfer to perform maintenance on an automobile air conditioner safely and easily. Some examples are described in U.S. Pat. No. 6,089,032; U.S. Pat. No. 6,446,453; and U.S. Pat. No. 6,467,283, all to Trachtenberg, the teachings of which are all herein incorporated by reference. These products include methods and kits for changing an air conditioning system over from using R-12 to R134a and a kit for servicing an air conditioning system.
The servicing kit of U.S. Pat. No. 6,446,453 includes a unitary hose connection for servicing an automobile air conditioning system. A first connector is disposed at one end and is connectable with a low pressure service port of an automobile air conditioning system, and a second connector is disposed at the other end of the hose and is selectively connectable with both a pressure gauge and a can tap valve. The can tap valve is attachable to a can of compressed refrigerant. When a pressure gauge is attached to the second connector and the first connector is attached to the service port, the pressure of the refrigerant in the automobile air conditioning system can be measured. When the second connector is attached to the can tap valve, the compressed refrigerant in the can may be introduced into the automobile air conditioning system to thereby service the system. The hose connection, pressure gauge, can tap valve, and can (or cans) of refrigerant may be packaged together in a kit.
While the above-described servicing system is quite useful for servicing an automobile air conditioner, it is still a little cumbersome to use, in that it requires at least two connections to be made in order to measure the pressure of the refrigerant in the air conditioner and add more refrigerant to the air conditioner. Every time the hose is removed from the port, a quantity of the pressurized gas spurts out of the hose, and air can enter the hose when it is disconnected. This enables air—and any impurities in the air—to be introduced into the air conditioner and threatens to lessen the performance of the system. Also, if a user is not careful when using the servicing kit and removes the pressure gauge while the hose is still attached to the service port, the refrigerant and oil will come shooting out of the system via the hose, invariably in the direction of the user. Thus, the servicing kit described is not quite “idiot-proof.”
Another drawback to conventional do-it-yourself systems is that it is difficult to know when one has added sufficient refrigerant. With the servicing kit of U.S. Pat. No. 6,446,453, one must repeatedly connect and disconnect the hose alternatively to the gauge and the container in order to check on the progress of the recharging of the system. Also, it is not very convenient to store any refrigerant remaining in the container. One must close the can tap valve completely and keep the valve connected to the can. Failure to close the can tap valve completely will result in the refrigerant leaking out of the container. Even when fully closed, they tend to leak.
Such a can tap valve is present in a recent U.S. Pat. No. 6,609,385 to Ferris et al. A disadvantage of such a system is that in order to close the can tap valve and stop the flow of refrigerant into the air conditioner, one must repeatedly turn the handle or knob of the valve until the valve is fully closed. This procedure can take several seconds, during which refrigerant continues to leave the container and enter the air conditioning system. In other words, if one wanted to stop adding refrigerant to the system at a given point, one would have to know what that point was in advance. (A similar system was sold by the instant assignee in the 1980s as model no. HA-20, in which a check valve was disposed in the piercing valve.). One cannot switch quickly between measuring the pressure in the system to adding additional refrigerant to the system and back again. It is also difficult to tell if the can tap valve has been fully closed when it is intended to be closed. Should the can tap valve be left partially open, the pressure readings on the gauge will be affected. Should the can tap valve be left partially open and the device be disconnected from the air conditioning system, the device will vent refrigerant into the atmosphere.
There is a need for a device to allow a typical consumer to measure the refrigerant pressure in his automobile air conditioner easily and safely and, if the level is low, to add additional refrigerant and possibly other chemicals such as leak detector, lubricant, etc.